Strong knots, weak knots... If you have much experience with ropes and knots, then you already know that knots are weaker than the ropes they're tied in. What you may not know is that various kinds of knots vary in how much they weaken the rope they're tied in. When I was in the Navy, I had to complete a course in “marlinspike seamanship” – basically, the art of tying knots. We learned by rote which knots were strong (that is, weakened the rope less) and which were weak (weakened the rope more), but I had no idea why. The problem has been studied, and the reasons identified.

By the way ... the single most important thing I learned from that marlinspike seamanship course was this: figure-eight knots are good.

This is what happens when you challenge engineers with tough problems: they come up with answers, and not necessarily what you'd expect. This team was challenged to make ships more efficient. They didn't take any of the obvious traditional approaches (change the hull shape, change the propulsion system, etc.). I'd love to know what piece of insight led to the idea of making the ship ride on a blanket of compressed air bubbles!